Experimental study and geometrical method to design bio-inspired robotic kinematic chains of inching-locomotion caterpillars.

Inching-locomotion caterpillars (ILAR) show impressive environmental adaptation, having high dexterity and flexibility. To design robots that mimic these abilities, a novel Bioinspired Robotic Design (BIROD) method is presented. The method is composed by an algorithm for Geometrical Kinematic Analysis (GEKINS) to standardize the proportional dimensions according to the insect's anatomy and obtain the kinematic chains. The approach is experimentally applied to analyze the locomotion and kinematic chain of these specimens: Geometridae - 2 pair of prolegs (represents 35,000 species) and Plusiinae - 3 pair of prolegs (represents 400 species). The obtained data indicate that the application of the proposed method permits to locate the attachment mechanisms, joints, links, and to calculate angular displacement, angular average velocity, number of degrees of freedom, and thus the kinematic chain. Geometridae in contrast to Plusiinae, shows a longer Walk-Stride Length (WSL), a lower number of single-rotational joints in 2-D (3 DOF versus 4 DOF), and a lower number of dual-rotational joints in 3-D (6 DOF versus 8 DOF). The application of BIROD and GEKINS provides the forward kinematics for 35,400 ILAR species and are expected to be useful as a preliminary phase for the design of bio-inspired arthropod robots.